Bad beef will have a sheen to it, like slime coating that is iridescent in the light. And a very pungent odor! If you had to get yoru nose very close it it to smell anything, it's just fine. Go ahead and use it. BTW: aged beef is refrigerated for 30 days at least after slaughter.
High CPK levels are an indicator of a variety of muscle diseases and problems, not just Rhabdo. The 'normal' CPK levels are between 25 and 170. Over this number, and you have muscle cell damage happening. You can have high(er) CPK levels and not have Rhabdomyolysis. You can have muscle cell death happening, and never get to Rhabdomyolosis. You have to have -enough- cell death and -enough- myoglobin and other toxic dead cell byproducts to overwheml the system.
Rhabdomyolysis occurs when there is damage to the skeletal muscle. The injured muscle cell leaks myoglobin (a protein) into the blood stream. Myoglobin can be directly toxic to kidney cells, and it can impair and clog the filtration system of the kidney. Both mechanisms can lead to kidney failure (the major complication of rhabdomyolysis). Significant muscle injury can cause fluid and electrolyte shifts from the bloodstream into the damaged muscle cells, and in the other direction (from the damaged muscle cells into the bloodstream). As a result, dehydration may occur.